Surface treating articles such as flap brushes, cleaning brushes, bristle brushes and convolute wheels are known. Exemplary of these surface treating articles are those available from the Minnesota Mining and Manufacturing Company of St. Paul, Minn. under the trade designation "Scotch-Brite". Flap brushes include a central core with a plurality of compressed radially extending strips or flaps of abrasive-containing nonwoven material. An edge of each flap is attached to the core while the opposing free edges of the compressed flaps form the outer working surface of the brush. Surface conditioning operations with these articles are accomplished by rotating the core while the working surface of the article is maintained in contact with a workpiece. Flap brushes may be used, for example, in the surface preparation and conditioning of metals, woods, plastics and other materials to prepare the surfaces for painting, plating, or the like as well as to impart a desired finish to the surface of a workpiece. The construction of other surface treating articles such as cleaning brushes, bristle brushes, convolute wheels and the like is similar to the aforementioned flap brushes in that all of these articles are made by attaching suitable surface treating segments such as flaps, discs or bristles, for example, to the outer peripheral surface of a rotatable core.
In the aforementioned articles, attachment of surface treating segments to a core may be accomplished by mechanical means and/or with a suitable adhesive. Although known mechanical attachments are relatively simple in their construction, they add weight to the finished article which, in turn, can cause rotational balancing problems in use. Additionally, the inclusion of mechanical attachments in the manufacture of surface treating articles can complicate manufacturing processes. Because of these difficulties, adhesives have been extensively employed as alternatives to mechanical fasteners in the manufacture of the foregoing articles.
Although the use of adhesives has been successful in overcoming many of the problems associated with mechanical attachments, other problems have arisen. A significant problem has been the formation of void spaces in the adhesive. To provide a strong adhesive bond resistant to failure during normal brush operation under high rotational forces, the bond line between the core and each of the surface treating segments must be substantially continuous (e.g., with no significant voids in the adhesive to serve as stress risers). In practice, however, voids of significant volume frequently occur within the core/segment bond line which, in turn, can result in a weakened bond that may cause adhesive failure when the finished article is later used. Moreover, such voids in the cured adhesive are difficult to detect due to the overall size of many surface treating articles. For example, depending on the intended use of the finished article, abrasive articles such as flap brushes and the like are manufactured to have a significant width (e.g., 0.5 meter or more), making an adequate inspection of the adhesive bond line between the core and the individual segments difficult at best. Accordingly, it is desirable to provide surface treating articles such as flap brushes, cleaning brushes, bristle brushes, convolute wheels and the like wherein the surface treating segments are attached to the core with an adhesive and wherein the adhesive is effective in forming a strong core/segment interface substantially free of objectionable void spaces.
Aside from the above described concerns relating to mechanical failure, additional aesthetic concerns are raised by the formation of voids in the core/segment interface. In the manufacture of the flap brushes, for example, the manufactured brush is often cut to a smaller size for certain applications. Cutting the manufactured article exposes a new portion of the core/segment interface that may or may not have a uniform and concentric adhesive bond line. The presence of visible void spaces in the adhesive interface may be considered undesirable for aesthetic reasons. Accordingly, it is desirable to provide surface treating articles such as flap brushes, cleaning brushes, bristle brushes, convolute wheels and the like wherein an adhesive is used in the attachment of the surface treating segments to the core and wherein the adhesive provides a strong and aesthetically acceptable interface between the segments and the core.
Efforts have been made to solve the problem of adhesive failure by making mechanical modifications to the construction of the core, for example, to promote the uniform application of adhesive over the core. Although these efforts have met with some success, it is desirable to provide a solution to the aforementioned problem without the need to substantially modify the mechanical components of the aforementioned surface treating articles. It is desirable to provide surface treating articles such as flap brushes, cleaning brushes, bristle brushes, convolute wheels and the like wherein an adhesive is used in the attachment of the surface treating segments to the core and wherein the adhesive is expansive in a molten or fluid state so that, when the surface treating segments are applied to the core member, the adhesive will expand into and around the segments to form a strong bond between the core member and the abrasive segments and wherein the expanded adhesive is substantially free of significant void spaces.